Manufacture of paper



May 1l, 1937. l.. B. ROGERS 2,080,362

MANUFACTURE OF PAPER Filed Jan. 25, 1955 2 Sheets-Sheet l .May 11, 1937. B ROGERS 2,080,362

MANUFACTURE OF PAPE R Filed Jan. 25,1955 2 sheets-sheet 2 /v VEN To R n zzfer. 7Eog r6 Patented May 1v1, 1937 PATENT OFFICE 2,080,362 MANUFACTURE or PAPER Luther B. Rogers, Methuen, Mass., assitnor to Champion-International Company, Lawrence, Mass., a corporation oi' Massachusetts Application January 25, 1935, Serial No. 3,531

8 Claims.

This invention relates to the manufacture of paper and more particularly to an eifectivecontrol of the moisture content in webs of coated paper, especially when of great width, that are continuously maintained as a flat ribbon from coating to winding and are dried while travelling at high speed with high temperature air.

A highly important factor controlling the proper condition of coated paper to be further processed is the moisture content. In the slower methods of drying coated paper, such as festooning, an operator skilled in the art may detect undesirable variations in the moisture content of the coated web by feel and thereupon make such changes in the controlling factors as to compensate for them, but only with great waste duc to having to 30 minutes of paper in the line.

It is obvious that when drying at high speeds,

as required herein, where in 1/2 to 1 minute of paper is in the line the skill of the operator is Wholly inadequate to detect any undesirable change in the moisture content before it is too late to correct it.

` The object of this invention is to malte certain that the value of the moisturecontent in the web of dried coated paper is continually kept within vsuch limits that further processing may be effected without injury, all while causing the web to travel through the dryer and to be Wound at the same high speed at which it travels through the coater. This isa problem that has heretofore remained unsolved. Those skilled in the art are well aware that the problem of controlling the moisture content in a web of paper that has once been dried and is then Wet again is entirely different and presents far greater diiiiculty in its solution than measuring during its manufacture of the amount of original water in a web of paper to be used as a base for a later coating operation.

I believe that I am the rst to make this application to that intermediate process in the manufacture of coated paper which has to do with the coating and drying thereof, and this invention embraces, therefore, a novel method of preparing coated paper continuously at high speeds in a, manner that eliminates substantial Waste from an excess or lack of moisture during further processing.

To the accomplishment of this object and such others as may hereinafter appear, as will readily be understood by those skilled in the art from the following description, the invention comprises the features and combinations of parts and the method of manufacture hereinafter described and then particularly pointed out in the' appended claims.

'I'he nature and scope of the invention will be understood from a description of the high speed paper coating, drying and winding apparatus 5 illustrated in the accompanying drawings, in which:

Figure 1 is a diagrammatic view, in side elevation and partly in section, of a standard practice paper coater for coating one side oi' a web l0 of paper and an approved paper Winder combined with one satisfactory form of straight line dryer intermediate the coater and Winder. Only enough of these elements are shown to illustrate a complete paper coating apparatus, the im- 163 provement of this invention, in such'an apparatus, being indicated by the circuit diagram and brushes engaging the dried web prior to winding;

Fig. 2 is a view, in elevation and diagrammatic in character, of a motor generator set of` a type which may conveniently be used to generate power for the purposes of this invention;

Fig. 3 is a diagrammatic view, in side elevation and partly in section, showing standard practice for applying the coating to both sides of a web of paper, that may be substituted for the one side coater illustrated in Fig. 1; and

Figs. 4, 5, and 6 are diagrammatic views of electrical equipment and connections used in the organization illustrated in either Fig. 1 or Fig. 2.

In the embodiment of the. invention illustrated in the drawings, with special reference to Fig. 1, the coating element of the organization is typical of standard practice including a supply roll 3 of dry paper from which the web W passes a brush 4 rotating in a pan 5 of coating material and thence, after having had the material applied by the brush to one side, over a belt 6 travelling across a table'l where a set of transversely reciprocating brushes 8 act on the wet face of the ,m web to evenly distribute the coating material applied by the brush 4.

From the coater the web of paper is led over suitably located idler rolls to a dryer and on emerging from the dryer to the web is wound all of which, under the improved conditions of this invention as will appear from this specification, is accomplished without reduction in the speed of travel of the web from coating to winding, while substantially eliminating Waste at iinishing due to the web being too wet or too dry at the calender, and notwithstanding the continuous advance of the web at these high speeds.

For the purposes of this disclosure the dryer to which the paper web is led from the coater may include an endless conveyer 20 of substantial length, for example approximating 'l5 feet in one good practical form, running in a drying chamber located within a dryer casing 24. The dryer, as shown, is so constructed that the floor 26 of the room in which it is located may form the bottom of its casing. Highly heated air is circulated rapidly around the conveyer and the moistened web oi paper carried labove and belowvit wet face outward. The accompanying drawingsare exemplary of a double-run iiat type dryer, since the web passes into and out of the drying chamber at the same end, but my invention is not After drying, y

limited to this particular type. the web passes to any satisfactory kind of Winder 23, the well known Pope reel being illustrated,

where the web is wound into a roll 30 for transfer to a calender for finishing.

The chief difficulty encountered in preparing coated paper for the finishing processes is that the ilnai surface finish of the paper is materiallyv affected by the degree of moisture in the web upon its delivery from the dryer preparatory to winding. This moisture content of the web is decidedly affected by a slight change in speed or temperature or humidity in the dryer, or the amount of water to be evaporated from the coating mix, or a change in the make-up or in the weight of the uncoated paper. In some coated papers as small a variation as 1/2 to 1% above or below an optimum moisture content will produce a -substantial diierence in the appearance of the nished paper. Too radical changes in the moisture content cause the web to change so in its characteristics that the machine ceases to make paper at all, a web too dry snaps oil at the calender due to shrinkage, and a web too wet wrinkles in the calender. Heavy loss results in both cases.

It has been determined by experiment that the success or failure of a high speed at dryer to produce uniformly dried coated paper is wholly dependent on the success attained in gaining knowledge, soon enough for correction, of variations in the moisture content prior to winding.

The method of this invention is eiective to this end by progressively detecting within very narrow limits, all without lag, whether the moisture content of the coated and dried paper is tending to unduly rise above or fall below an optimum moisture content predetermined as proper for the run of paper through the coating equipment, and by accurately indicating to the voperator all such variations whether -they be so small that they may be neglected or of such changing value that correction is required. Heretofore the moisture content of the paper has usually been corrected by resorting to changing the temperature of the air which dries the sheet, or changing the speed of circulation of the air. I have discovered that the most effective way of accomplishing this resuit, and the one completely responsive to the kind of moisture content testing means required for the high speeds essential to this invention, is toincrease or decrease the length of the drying period to which any given portion of the web will be subjected. This is most easily accomplished by changing the rate of travel of the paper web through the dryer.

As shown in Fig. l, the rubber belt 6 and the endless conveyer 20 are both driven through suitable belt connections from an electric motor 32. The reel 28 is similarly driven by another electric motor 33. These two motors are connected in parallel inthe line of a direct current 'rately excite the generator 34. ,i Accordingly the motor generatorset just referred to includes an exciter 36 directly connected to the motor 35 and the direct current generator 34 to which it supplies exciting current. Fig, 5 shows diagrammatically the circuits supplied by the exciter, the field coil for the generator`34 being indicated at 34 and the shunt field coils for the motors 32 and 33 being indicated at 32' and 33', respectively. Connected in series with the field coil 36 of the exciter is a rheostat 31 and additional rheostats 38, 39, and 40 are connected in series with the shunt fields of the generator 34, the motor 32 and the motor 33, respectively. As will be evident to those skilled in the use of electrical equipment of this general character, it is possible, by suitably adjusting the rheostats 31 and 38, to vary the voltage of the generator 34 through a wide range and thus to correspondingly vary the speeds of both the motors 32 and 33. In addition, the motor speeds may be further varied by to include, in series with the field of the reel,

motor 33, a vernier rheostat 4I, the total resistance of which may be approximately equal to or slightly greater than the resistance between adjacent points of the main field rheostat 40.

As hereinbeiore stated a small variation in the moisture content of the dried web produces such a variation in the electrical resistance of the coated paper as to enable detection by a suitable instrument for measuring ohmic resistance. Accordingly such an instrument has been provided for continuously testing the insulating value of the web after it has left the dryer.

For the purpose of measuring the electrical resistance or insulating value of the dried web, it has been found possible to use an insulation testing instrument, such as that known as a Megger, and to make this measurement as the dried which includes a needle 45 arranged to swing oyer a scale 46. Cooperating with, and forming part of both of these units, are two permanent magnets 41-41 winch supply the magnetic fields required in both units. One side of the generator is connected to a brush 48 which is grounded on the roll 42, while the other side of the generator is connected through a resistance 5I! to a bar 5I (Figs. 1 and 6) carrying a series of metal strips or brushes 52 which bear on the surface of the web W approximately across lthe entire width of the sheet. The current owing through this circuit is extremely small even under a voltage of approximately five hundred, :which has been found suitable for this testing operation, and it 75 flows through a movable coil A in the armature of the instrument Il. Two other coils B and C are connected in series with each other and with the resistance 53 directly across the generator line so that for any given generator voltage the current iiowing through these coils is constant. The angular relationship of these coils to the coil A and to the flux flowing through this part of the instrument is such that the pointer 45 which is connected rigidly to the coil A will always move to the same reading on the scale for a given resistance under test which may be arranged for measuring any part or all of the width of the web through one or all of the contacts 52, notwithstanding even substantial variations in the potentialcreated by the generator. This instrument is so well known that no detailed description of it is necessary here.

It has been determined, however, that with such an instrument variations of a small fraction of 1% in moisture content of the web W will be indicated on the scale 46 by the pointer l5. Consequently, it is a simple matter tocalibrate the instrument and predetermine the proper scale reading for the optimum moisture content of the paper. In practice the needle 45 utters continuously but its movement may not be such as to indicate that the moisture content of the paper is outside of the tolerance within which the paper may be successfully finally processed. Under such indications no change in the factors governing the process need be made.

When tle,h operator sees the needle 45 consistently drop below the calibrated reading, he knows that the moisture content of the web is unduly rising, and by turning the rheostat 38 to the proper direction he can lower the generator voltage more or less, as circumstances require, and thus reduce the rate of travel of the web through the coating equipment. These changes in speed, which can be made almost instantaneously, will result in increasing the drying effect thus bringing the- Web to the testing Apoint with a lower moisture content. On the other hand, lf the needle t consistently rises above the calibrated reading, indicating that the moisture content of the web is unduly falling, the operator makes an opposite adjustment of the rheostat 38, thus increasing the rate of speed of the conveyer and decreasing the drying effect. Constant and highly accurate information is given as to the amount of moisture in the moving web and the proper changes in the process may immediately be made to anticipate and correct or compensate for incipient undesirable variations of the moisture content from the desired optimum.

The apparatus of Fig. 1 illustrates coating the paper on one side only. 'I'he invention is equally efcient when the paper is coated on both sides. For coating on both sides, the web W', unwound from a roll 3', may be guided into and through a coating bath in a pan 5 and thence through a pair of driven squeeze rolls G'8. From the squeeze rolls the web passes through upper and lower sets of reciprocating brushes 9 which spread the coating material evenly on both surfaces of the web. From this point the web travels to the upper run of the conveyer 20 within the dryer (Fig. l) but on its way to this member it is desirable to support the web by jets of hot air directed upwardly through the perforated surfaces of air ducts 55-55 which can be supplied in any convenient manner as by a motor driven blower 56. By the time the web reaches the conveyer 2B the coating on its lower surface has been dried suiiiciently to prevent injury by its contact with the web supporting elements of the tively driven by a belt connection which also drives the conveyer as illustrated in Fig. 1.

The nature and scope of the invention having been indicated, and the preferred manner of practising the process enabled by apparatus like that disclosed having been specifically described, what is claimed as new, isz- 1. The method of manufacturing paper which comprises coating a web of paper, drying said coated web at highspeed, testing said web by determining the normal insulating value thereof at its optimum moisture content, after it has been dried, and then calendering said web while at its determined optimum moisture content.

2. The method of manufacturing paper which comprises coating a web of paper,A drying said coated web at high speed, testing said web by determining the normal insulating value thereof at its optimum moisture content, after it has been dried, winding said web while the web advances continuously and uninterruptedly from coating to winding, and thereafter calendering said web, while said web is at its determined optimum moisture content.

3. The method of manufacturing paper which comprises coating a. web of paper, drying said coated web at high speed, measuring the insulating value of the web by an electric current at relatively high potential after said web has been dried, and continuously and without lag indicating variations from the optimum condition of the web as uninterruptedly determined by said measure whereby compensatory changes in the preparatory process may be made as required by any indication of undue variation, and then calendering said web while at its determined optimum condition.

4. The method of manufacturing paper which comprises coating a web of paper, drying said coated web at` high speed, measuring the insulating value of the webafter the web has been dried, and continuously and without lag indicating variations from the optimum condition of the web as uninterruptedly determinedby said measure whereby compensatory changes in the preparatory process may be made as required by the indication of any undue variation, winding said web and thereafter calendering the web, while said web is at its determined optimum condition.

5. In the manufacture of coated paper wherein a paper web advances uninterruptedly and at high speeds from coating to winding, the method of controlling the moisture in the paper of the moving web within manufacturing tolerance from the optimum moisture content which includes `the steps of coating with a wet mix, drying at high speed and winding, all without reduction in the speed of travel at which the web leaves the coater and while the web remains as a fiat ribbon from coater to Winder, constantly determining the moisture in the paper of the running web by measuring the insulating value of the web, through the web, at the dry end of the drying step, and prior. to winding, and continuously and without lag, indicating variations of the moisture content from the optimum as uninterruptedly determined by such measure, whereby such compensatoryv changes in the preparatory Vprocess as may be required by the indication of an 'undue variation may be made, and then calendering said web while at its optimum moisture content.

6. Inthe manufacture of coated paper wherein a paper web advances uninterruptedly and at high speeds from coating to winding, the method of controlling the condition of the paperV in the moving ,web within manufacturing tolerance from an optimum condition which includes the steps of coating, drying at high speed and winding, all

-without reduction in the speed of travel at which the web leaves the coater, andconstantly determining the optimum condition ot the paper oi the running web by measuring the insulating value thereof, at the dry end of the drying step, and continuously and without lag indicating variations from the optimum as uninterruptedly determined by said measure, whereby operations prior to winding may be modified as required by departures from the normal insulating value of the web, and then calendering said web, while said web is at its determined optimum condition.

'7. The method of manufacturing paper which comprises coating a web of paper and then drying `and winding said web of paper while the web advancescontinuously and uninterruptedly at high speed from coating to winding, determining the normal insulating value 4of the dried web at its optimum condition, anticipating any tendency of the drying operation to unduly change said optiacsasea v mum condition, by continuously and without lag measuring the insulating value of the dried web at the dry end of the drying step, prior to winding, and indicating any tendency to vary from the norm, whereby operations prior to winding may be modified as required by departures from the normal insulating value of the web, and then ialendering said web while at its optimum condi- 8. 'I'he method of manufacturing paper which comprises coating a web o! paper and then drying and winding said web of paper while the web.advances continuously and uninterruptedly at high speed from coating `to winding, determining the normal insulating value of the dried web at its optimum moisture content, anticipating any tendency of the drying operation to unduly increase or decrease said optimum moisture content by continuously and without lag measuring the insulating value of the dried web through the web at the dry end of the drying step, prior to winding, and indicating any tendency to vary from the norm, whereby operations prior to' winding may be modified as required by departures from the normal insulating value oi the web before the moisture content can reach a value that would be injurious in further processing, and then calendering said web at its determined optimum moisture content.

- LUTHER B. ROGERS. 

